An oil well typically collects approximately 30 percent of its oil from an underground oil reservoir during the primary recovery phase. An additional 20 percent of the oil may be recovered using secondary recovery techniques, such as water flooding that raises the underground pressure. Enhanced oil recovery (“EOR”) provides a tertiary recovery technique capable of recovering an additional 20 percent or more of the oil from the underground reservoirs.
During the EOR process, large quantities of gas are injected into the underground oil reservoir, thereby urging additional oil from the well. Carbon dioxide is typically used as the EOR gas due to its ability to mix with the underground oil and render the oil less viscous and more readily extractable.
Much of the carbon dioxide injected into the oil well is recovered with the recovered oil. However, the recovered carbon dioxide typically contains significant quantities of other constituents, such as water vapor, methane, ethane, propane, butane and pentane. Reuse of carbon dioxide contaminated with these constituents in the EOR process is believed to significantly reduce operating efficiency.
Existing separation techniques, such as amine separation, solvent separation and molecular sieve separation, are inefficient for separating carbon dioxide from gaseous oil well effluent due to the relatively high percentage of carbon dioxide in the effluent. Other techniques, such as oxygen burning, waste the hydrocarbon resource in the effluent.
Accordingly, those skilled in the art continue with research and development efforts in the field of carbon dioxide separation from gaseous oil well effluent.